Reading HTTP headers in a Spring REST controller

Question

I am trying to read HTTP headers in Spring based REST API. I followed this. But I am getting this error:

No message body reader has been found for class java.lang.String,
ContentType: application/octet-stream

I am new to Java and Spring so can't figure this out.

This is how my call looks like:

@WebService(serviceName = "common") @Consumes({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON }) @Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON }) public interface CommonApiService {      @GET     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)     @Produces(MediaType.APPLICATION_JSON)     @Path("/data")     public ResponseEntity<Data> getData(@RequestHeader(value="User-Agent") String userAgent, @DefaultValue ("") @QueryParam("ID") String id); } 

I have tried @Context: HTTPHeader is null in this case.

How to get values from HTTP headers?

Answer 1

The error that you get does not seem to be related to the RequestHeader.

And you seem to be confusing Spring REST services with JAX-RS, your method signature should be something like:

@RequestMapping(produces = "application/json", method = RequestMethod.GET, value = "data") @ResponseBody public ResponseEntity<Data> getData(@RequestHeader(value="User-Agent") String userAgent, @RequestParam(value = "ID", defaultValue = "") String id) {     // your code goes here } 

And your REST class should have annotations like:

@Controller @RequestMapping("/rest/") 

Regarding the actual question, another way to get HTTP headers is to insert the HttpServletRequest into your method and then get the desired header from there.

Example:

@RequestMapping(produces = "application/json", method = RequestMethod.GET, value = "data") @ResponseBody public ResponseEntity<Data> getData(HttpServletRequest request, @RequestParam(value = "ID", defaultValue = "") String id) {     String userAgent = request.getHeader("user-agent"); } 

Don't worry about the injection of the HttpServletRequest because Spring does that magic for you ;)

Answer 2

I'm going to give you an example of how I read REST headers for my controllers. My controllers only accept application/json as a request type if I have data that needs to be read. I suspect that your problem is that you have an application/octet-stream that Spring doesn't know how to handle.

Normally my controllers look like this:

@Controller public class FooController {     @Autowired     private DataService dataService;      @RequestMapping(value="/foo/", method = RequestMethod.GET)     @ResponseBody     public ResponseEntity<Data> getData(@RequestHeader String dataId){         return ResponseEntity.newInstance(dataService.getData(dataId);     } 

Now there is a lot of code doing stuff in the background here so I will break it down for you.

ResponseEntity is a custom object that every controller returns. It contains a static factory allowing the creation of new instances. My Data Service is a standard service class.

The magic happens behind the scenes, because you are working with JSON, you need to tell Spring to use Jackson to map HttpRequest objects so that it knows what you are dealing with.

You do this by specifying this inside your <mvc:annotation-driven> block of your config

<mvc:annotation-driven>     <mvc:message-converters>         <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">             <property name="objectMapper" ref="objectMapper" />         </bean>     </mvc:message-converters> </mvc:annotation-driven> 

ObjectMapper is simply an extension of com.fasterxml.jackson.databind.ObjectMapper and is what Jackson uses to actually map your request from JSON into an object.

I suspect you are getting your exception because you haven't specified a mapper that can read an Octet-Stream into an object, or something that Spring can handle. If you are trying to do a file upload, that is something else entirely.

So my request that gets sent to my controller looks something like this simply has an extra header called dataId.

If you wanted to change that to a request parameter and use @RequestParam String dataId to read the ID out of the request your request would look similar to this:

contactId : {"fooId"}  

This request parameter can be as complex as you like. You can serialize an entire object into JSON, send it as a request parameter and Spring will serialize it (using Jackson) back into a Java Object ready for you to use.

Example In Controller:

@RequestMapping(value = "/penguin Details/", method = RequestMethod.GET) @ResponseBody public DataProcessingResponseDTO<Pengin> getPenguinDetailsFromList(         @RequestParam DataProcessingRequestDTO jsonPenguinRequestDTO) 

Request Sent:

jsonPengiunRequestDTO: {     "draw": 1,     "columns": [         {             "data": {                 "_": "toAddress",                 "header": "toAddress"             },             "name": "toAddress",             "searchable": true,             "orderable": true,             "search": {                 "value": "",                 "regex": false             }         },         {             "data": {                 "_": "fromAddress",                 "header": "fromAddress"             },             "name": "fromAddress",             "searchable": true,             "orderable": true,             "search": {                 "value": "",                 "regex": false             }         },         {             "data": {                 "_": "customerCampaignId",                 "header": "customerCampaignId"             },             "name": "customerCampaignId",             "searchable": true,             "orderable": true,             "search": {                 "value": "",                 "regex": false             }         },         {             "data": {                 "_": "penguinId",                 "header": "penguinId"             },             "name": "penguinId",             "searchable": false,             "orderable": true,             "search": {                 "value": "",                 "regex": false             }         },         {             "data": {                 "_": "validpenguin",                 "header": "validpenguin"             },             "name": "validpenguin",             "searchable": true,             "orderable": true,             "search": {                 "value": "",                 "regex": false             }         },         {             "data": {                 "_": "",                 "header": ""             },             "name": "",             "searchable": false,             "orderable": false,             "search": {                 "value": "",                 "regex": false             }         }     ],     "order": [         {             "column": 0,             "dir": "asc"         }     ],     "start": 0,     "length": 10,     "search": {         "value": "",         "regex": false     },     "objectId": "30" } 

which gets automatically serialized back into an DataProcessingRequestDTO object before being given to the controller ready for me to use.

As you can see, this is quite powerful allowing you to serialize your data from JSON to an object without having to write a single line of code. You can do this for @RequestParam and @RequestBody which allows you to access JSON inside your parameters or request body respectively.

Now that you have a concrete example to go off, you shouldn't have any problems once you change your request type to application/json.